Rotary drum washer

ABSTRACT

A system and method for recycling a waste glass cullet includes a first screening station for separating large glass shards of approximately one inch in diameter from smaller glass shards in the cullet, a crusher to reduce the large glass shards to smaller glass shards smaller than approximately one inch in diameter, a second screening station to separate remaining large contaminants having a diameter of approximately one inch or greater from the cullet, a series of vacuum inlets disposed along a conveyor to remove light contaminants, a presoaking apparatus comprising a holding tank partly filled with a presoaking solution, a rotary washing apparatus comprising a drum with vanes disposed along an inner wall of the drum to toss the cullet in the washing solution, the vanes being oriented so that the cullet is tossed progressively forwardly toward a discharge outlet of the drum, to remove buoyant contaminants from the cullet, a dewatering apparatus to remove excess water from the cullet, and a dryer for reducing the moisture content of the cullet. The system and method may further include a second rotary crusher for reducing the cullet size to 12 mesh or smaller and a vibratory multi-deck screen to separate the crushed glass cullet into specified particle sizes. In the preferred embodiment the rotary drum washer for includes a rotating drum having one or more vanes disposed along an inner wall of the drum to toss the cullet in the washing solution, the vanes being oriented so that the cullet is tossed progressively forwardly toward a discharge outlet of the drum.

This application is a divisional of application Ser. No. 09/010,033filed Jan. 21, 1998, U.S. Pat. No. 5,950,936.

FIELD OF THE INVENTION

This invention relates to a system and process for recycling glass. Inparticular, this invention relates to a system and process for recyclingglass cullet to a purity suitable for re-use in industrial applications,requiring only preliminary separation of waste from the cullet prior torecycling.

BACKGROUND OF THE INVENTION

The benefits of recycling materials are well known. Most commonhousehold materials, including paper, metals and glass, can be recycledfor re-use by industry. However, the cost of recycling varies dependingupon the material.

Recycling of glass in particular has been a costly process. The mainreason is that industries which use recycled glass require that theglass be largely contaminant free. Household waste recycling programsgenerally do not discriminate between glass and ceramic recyclables, orbetween glasses of different colours. As such, glass recyclablescollected by recycling authorities tend to be a mixture of differentcolours of glasses and ceramics, as well as contaminants such as foil orpaper labels and any non-recyclable refuse that finds its way into abottle or jar or other refuse in a recycling bin.

These contaminants present a problem in conventional recyclingprocesses. Prior to the invention there has not been a satisfactorymethod available for eliminating contaminants such as small paper andfoil particles and chemical adhesives from the recycled glass. Thesecontaminants render the recycled glass unsuitable for use in manyindustrial processes.

Moreover, the ceramic content of the mixture presents a particularproblem, because ceramic does not burn off at temperatures which willeliminate most other contaminants and it is often difficult tophysically distinguish ceramic from glass so it is virtually impossibleto eliminate the ceramic content of the mixture prior to processing.However, recycled glass with any significant content of large ceramicparticles is useless to many industries, for example bottle production,because these particles weaken the structure of the recycled product.

As such, existing recycling programs cannot recover much of the glasswhich is collected for recycling and end up disposing of it in landfillsites with other non-recoverable refuse.

The present invention provides a system and method for recycling glassfrom a three-mix cullet which includes whole and broken glassrecyclables of any colour as well as ceramics and other contaminants.The system and method of the invention requires minimal preliminaryseparation of materials, saving time and labour costs. The recycledglass cullet is over 99% contaminant free, which is acceptable for usein most industries, and can be produced in a powder form particularlysuitable for producing glass fiber insulation, sand blastingslurries,water filtrates, glass beads for reflective paint and manyother uses. The recycled glass is also environmentally safe and does notcause silicosis, even in powder form.

The invention accomplishes this by crushing the three mix cullet to asize at which the glass and ceramic can be separated from metal, plasticand other contaminants, washing the resulting mixture in a rotary drumapparatus to remove adhesives and other buoyant or “floatable”contaminants, heating the washed mixture to eliminate any remainingcombustibles and reduce moisture content, and optionally furthercrushing the glass particles to a particle size of minus 12 mesh.

It has been found that ceramics when reduced to a particle size of lessthan 20 mesh do not adversely affect recycled glass. Ceramic particlesof this size dissipate in industrial furnaces and do not form part ofthe recycled product. Thus, it becomes unnecessary to eliminate ceramicsfrom the recycling mixture, so long as they are crushed to the requiredsize so that they no longer form contaminants in the recycled product.By virtually eliminating contaminants such as paper, foil, ferrous andnon-ferrous metals and chemical adhesives, recycled glass produced bythe invention is suitable for reuse in most industrial applicationswhich would otherwise be unable to use recycled glass.

The invention further provides a novel glass washing apparatus,comprising a rotating drum having vanes disposed along its interiorwall. The drum is composed of sections, each section being supported byrollers and being differentially rotated by a drive mechanism to reducewear caused by misalignment of the drum on the rollers. As the drumrotates the glass slurry is tossed forwardly by the vanes, andprogressively conveyed toward the discharge outlet. The abrasion of theglass particles against the vanes and against neighbouring particles inthe presence of the wash solution removes any adhering buoyantcontaminants.

The present invention thus provides a system for recycling a waste glasscullet, comprising a first screening station for separating large glassshards of approximately one inch in diameter from smaller glass shardsin the cullet, a crusher to reduce the large glass shards to smallerglass shards smaller than approximately one inch in diameter, a secondscreening station to separate remaining large contaminants having adiameter of approximately one inch or greater from the cullet, a presoakholding tank partially filled with a presoaking solution, a rotarywashing apparatus comprising a drum having a vane disposed along aninner wall of the drum to toss the cullet in a washing solution, thevane being oriented so that the cullet is tossed progressively forwardlytoward a discharge outlet of the drum, to remove buoyant contaminantsfrom the cullet, a dewatering apparatus to remove excess water from thecullet, and a dryer for reducing the moisture content of the cullet.

The present invention further provides method of recycling a waste glasscullet, comprising the steps of separating large glass shards ofapproximately one inch in diameter from smaller glass shards in thecullet, crushing the large glass shards to smaller glass shards smallerthan approximately one inch in diameter, separating large contaminantshaving a diameter of approximately one inch or greater from the cullet,presoaking the cullet in a presoaking solution, washing the cullet in arotary washing apparatus comprising a drum with a vane disposed along aninner wall of the drum to toss the cullet in a washing solution, thevane being oriented so that the cullet is tossed progressively forwardlytoward a discharge outlet of the drum, to remove buoyant contaminantsfrom the cullet, dewatering the cullet to remove excess water, andreducing the moisture content of the cullet.

The present invention further provides a rotary drum washer for cleaninga solid material in a washing solution, comprising a rotating drumhaving an inner wall, a helical vane having an outer edge disposed alongthe inner wall of the drum and an inner edge remote from the inner wallof the drum, the vane being oriented so that the solid material istossed progressively forwardly toward a discharge outlet of the drum,and a plurality of radially oriented paddles extending between sectionsof the vane, each paddle having an outer edge disposed along an innerwall of the drum and an inner edge remote from the inner wall of thedrum, wherein the inner edges of at least some of the paddles extendtoward an axial center of the drum beyond the inner edge of the vanealong substantially an entire length of the paddles.

The present invention further provides a system for recycling glasscomprising rotary drum washer for removing buoyant contaminants fromglass cullet, the rotary drum washer comprising a rotating drum havingan inner wall, a helical vane having an outer edge disposed along theinner wall of the drum and an inner edge remote from the inner wall ofthe drum, the vane being oriented so that the cullet is tossedprogressively forwardly toward a discharge outlet of the drum, and aplurality of radially oriented paddles extending between sections of thevane, each paddle having an outer edge disposed along an inner wall ofthe drum and an inner edge remote from the inner wall of the drum,wherein the inner edges of at least some of the paddles extend toward anaxial center of the drum beyond the inner edge of the vane alongsubstantially an entire length of the paddles.

BRIEF DESCRIPTION OF THE DRAWINGS

In drawings which illustrate by way of example only a preferredembodiment of the invention,

FIGS. 1A, 1B, 1C and 1D are a schematic diagram showing the glassrecycling system of the invention,

FIG. 2 is a side elevation of a preferred embodiment of the rotary drumwasher,

FIG. 3 is a top plan view of the rotary drum washer of FIG. 2,

FIG. 4 is a cross-section of the rotary drum washer of FIG. 2, and

FIG. 5 is a side elevation of a preferred embodiment of a rotary screwconveyor for the system of the invention.

DETAILED DESCRIPTION OF THE INVENTION

A preferred embodiment of the glass recycling system of the invention isillustrated in FIG. 1. Raw recyclables are collected by civic or otherauthorities and transported to the recycling plant where they are storeduntil ready for processing. The recycling system and process comprisesthe following stages:

a) Feeding of raw material to a manual or mechanical sorting station—Theraw recyclables are loaded into a conventional vibratory feeder 3 whichfeeds the raw material at a selected rate to a manual or mechanicalsorting station 4 for separation of large contaminants.

b) Sorting—At the manual or mechanical sorting station 4 largecontaminants such as plastic bottles, metal, aluminum, ceramics stonesand the like are manually or mechanically removed from the raw mixtureand discarded into bins. The remaining three-mix cullet (referring tothe three colours of glass in the mixture) is placed onto a conveyor 5and conveyed to the first screening station 6.

c) First screening—At the first screening station 6 a conventionalvibratory screen filter with a 1 inch filter mesh separates large glassshards having a diameter of approximately 1 inch or greater from themixture. Glass shards and particles smaller than approximately 1 inchdrop into a second screening station 8. A magnetic head pulley 6 a ispreferably provided near the top of the infeed conveyor to the firstroll crusher 7, to remove large ferrous contaminants such as bottle capsprior to primary crushing.

d) First crushing—The larger shards having a diameter of 1 inch orgreater remaining in the first screening station 6 are fed into a firstroll crusher 7 and reduced to shards and particles smaller than 1 inch,which are then deposited into the second screening station 8.

e) Second screening—At the second screening station 8 anotherconventional vibratory screen filter with a 1 inch filter mesh separatesany large contaminants having a diameter of 1 inch or greater from themixture, such as plastic caps, bottle labels etc. which are notsignificantly reduced in size by the roll crusher 7. At this stage allparticles larger than 1″ are contaminants and are discarded into bins.

f) Air vacuuming—Glass shards and particles, and any remainingcontaminants smaller than 1 inch, drop onto a second conveyor 8 a. Airvacuum inlets 8 b disposed at selected points along the conveyor 8 aremove any light contaminants (paper, foil etc.) smaller than 1 inchprior to presoaking.

g) Presoaking—The presoak holding tank 30 is partially filled withrecirculated filtered water from the washing stage, to which a smallamount of fresh water is added to reduce stagnation. A commerciallyavailable surfactant cleansing agent is introduced to the holding tank30 to dissolve glues and foreign compounds adhering to the glass shardsprior to the washing stage. An infeed rotary screw conveyor 10,comprising an auger 20 axially disposed within cullet trough 32 similarto the conveyor illustrated in FIG. 5 but oriented horizontally at thebase of the presoak holding tank 30, regulates the feed of the glassshards, water and surfactant mixture (washing solution) into the rotarydrum washer 11 at a rate controlled by the drum rotation speed.

h) Washing—The washing solution is fed into the holding tank 30 throughcullet inlet 32, and drains into the drum 40 along with the glasscullet. As the drum 40 rotates paddles 51 disposed along the inner wallof the drum 40 toss the cullet in the washing solution. Abrasion of theglass particles against the paddles 51 and against neighbouring glassparticles in the presence of the surfactant removes any remainingadhering contaminants such as label paper or foil, adhesives, dirt etc.A helical vane 50 is provided along the inner wall of the drum 40 sothat the glass mixture is tossed progressively forwardly toward thecullet discharge outlet 44 of the drum 40.

All remaining buoyant or “floatable” contaminants are eliminated duringthe washing process and are discharged with the washing solution,preferably into a filter unit (not shown) which filters the washingsolution for reuse. The glass cullet now consists of cleaned,three-colour glass shards 1 inch or less in diameter.

i) Dewatering—The cleaned glass cullet is discharged from the drum 40into a vibratory dewatering screen conveyor 12, which removes excesswater from the mixture (the water is preferably filtered andrecirculated through the rotary drum washer 11). Alternatively, anotherrotary screw conveyor 10 such as the conveyor 10 illustrated in FIG. 5can be used to convey the cleaned glass mixture to the dryer 13 fordrying. In this embodiment the rotary screw conveyor 10 is preferablyinclined upwardly from inlet 24 to outlet 26, as shown in FIG. 5,allowing excess water to flow down the trough 22 toward a waterdischarge port 28 near the cullet inlet 24.

j) Drying—The dewatered glass cullet is discharged into a hopper feedinga vibrating float dryer 13 which distributes the glass particles evenlyon a dryer bed, preferably a “W” shaped dryer bed which allows theheated air blown through the bed to disperse to all surfaces of theglass particles. An example of a suitable dryer 13 is known as a“fluidized bed dryer” made by Carrier Vibrating Equipment Inc. Themixture is dried, preferably to reduce the moisture content to 0.5% orless, and any remaining residue of combustible or flammable particles isburned off and suctioned off by a conventional air vacuum system (notshown) into a suitable commercially available dust collector (notshown).

k) Storage of the recycled glass powder—The cleaned glass cullet isdischarged from the vibrator screen 16 to a conveyor 17, which conveysthe cullet to a bucket elevator feed 19 for deposit into storage silos20.

If a fine glass powder is desired, the system and method of theinvention may optionally include the following stages:

l) Second crushing—The dried cullet is discharged from the dryer 13 to aconveyor 13 a which conveys the cleaned mixture to a vibratory surgerhopper 14 that discharges the cullet in metered amounts into a secondcrusher 15, preferably a rotary rock on rock crusher, which crushes thecullet to a particle size of between plus 12 mesh and minus 12 mesh.

m) Second separation—The crushed cullet may be conveyed to a multi-deckvibrator screen 16 having a plurality of spaced apart minus 12 mesh andsmaller filters. Particles of the selected sizes (plus 12 mesh andsmaller) are discharged from the vibrator screens 16 to separateconveyors 17, which convey the glass powders to bucket elevator feeds 19for deposit into storage silos 20 according to particle size.

n) Re-crushing—All particles larger than the desired particle size aredischarged from the vibrator screen 16 to a recirculatory conveyor 18which conveys the cullet back to the rotary rock on rock crusher 15 forfurther crushing along with the continual discharge of glass cullet fromthe surger hopper 14.

The rotary drum washer 11, illustrated in FIGS. 2 to 4, comprises aholding tank 30 in communication with a steel drum 40 through a cullettrough 32. The drum 40 is preferably composed of three sections 42welded together or otherwise suitably joined along seams 42 a and weldedto ends 46. The sections 42 are each independently supported by sets offree-rolling support rollers 60 and drive rollers 62 disposed near eachseam 42 a. The rollers 60, 62 are mounted on posts 61 embedded in theconcrete slab floor 4. Preferably a separate hydraulic drive unit 66drives each set of drive rollers 62 independently, as shown in FIGS. 2and 3, reducing wear on the rollers 60, 62 caused by normal misalignmentof the drum sections 42 and undulation during use.

The washing solution is pumped into the holding tank 30 through fluidinlet 34, and drains into the drum 40 through the cullet inlet 32. Ahelical stainless steel vane 50 is disposed along the inner wall 40 a ofthe drum 40, as shown in phantom in FIG. 2, so that as the drum 40rotates the cullet migrates progressively forwardly toward the outlet44. The rotary speed of the drum 40 thus determines the duration of thewashing cycle, which can be adjusted depending upon the desiredrecycling capacity, surfactant concentration and water temperature toensure that the cullet is substantially cleaned of contaminants beforeegressing from the drum 40.

The interior of the drum 40 further includes a series of generallyrectangular paddles 51 oriented radially, preferably every 120° alongthe vane 50, as shown in FIG. 4, so that as the drum 40 rotates thecullet is tossed in the washing solution and drops back to the level ofthe washing solution as each paddle 51 approaches the top of therotational cycle of the drum 40.

The helical vane 50 has an outer edge disposed along the inner wall ofthe drum 40 and an inner edge remote from the inner wall of the drum 40.The plurality of radially oriented paddles 51 extend between sections ofthe vane 50, and each paddle 51 has an outer edge disposed along aninner wall of the drum and an inner edge remote from the inner wall ofthe drum 40, whereby the inner edges of at least some of the paddles 51extend toward an axial center of the drum beyond the inner edge of thevane along substantially the entire length of the paddles 51.

The “floatable” contaminants, including paper and foil label particlesand adhesive residues, float to the top of the solution and aredischarged with the solution through annular water discharge outlet 54surrounding the cullet outlet 44, preferably into a filter apparatus(not shown) which cleans the solution for reuse in the washing andpresoaking stages.

The washed cullet retains its ceramic content. To render the culletsuitable for use in industries which require that the ceramics beeliminated, the second crushing stage described above is employed toproduce a fine glass powder. The fine ceramic particles dispersedthroughout the glass powder will dissipate in further processing.

A preferred embodiment of the invention having been thus described byway of example only, it will be apparent to those skilled in the artthat certain modifications and adaptations may be made without departingfrom the scope of the invention, as set out in the appended claims.

What is claimed is:
 1. A rotary drum washer for cleaning a solidmaterial in a washing solution, comprising a rotating drum having aninner wall, a helical vane having an outer edge disposed along the innerwall of the drum and an inner edge remote from the inner wall of thedrum, the vane being oriented so that the solid material is tossedprogressively forwardly toward a discharge outlet of the drum, and aplurality of radially oriented paddles extending between sections of thevane, each paddle having an outer edge disposed along an inner wall ofthe drum and an inner edge remote from the inner wall of the drum,wherein the inner edges of at least some of the paddles extend toward anaxial center of the drum beyond the inner edge of the vane alongsubstantially an entire length of the paddles.
 2. The rotary drum washerof claim 1 in which the radially oriented paddles are disposedcircumferentially approximately 120 degrees apart.
 3. The rotary drumwasher of claim 1 comprising an inlet at one end thereof.
 4. The rotarydrum washer of claim 3 comprising a fluid outlet at an opposite endthereof.
 5. The rotary drum washer of claim 4 in which the vane extendssubstantially between the fluid inlet and the fluid outlet.
 6. Therotary drum washer of claim 3 in which the inlet is in communicationwith a hopper.
 7. The rotary drum washer of claim 6 for washing a glasscullet.
 8. The rotary drum washer of claim 1 in which the drum isrotated by external rollers in communication with a drive mechanism andwith an exterior wall of the drum.
 9. A system for recycling glasscomprising rotary drum washer for removing buoyant contaminants fromglass cullet, the rotary drum washer comprising a rotating drum havingan inner wall, a helical vane having an outer edge disposed along theinner wall of the drum and an inner edge remote from the inner wall ofthe drum, the vane being oriented so that the cullet is tossedprogressively forwardly toward a discharge outlet of the drum, and aplurality of radially oriented paddles extending between sections of thevane, each paddle having an outer edge disposed along an inner wall ofthe drum and an inner edge remote from the inner wall of the drum,wherein the inner edges of at least some of the paddles extend toward anaxial center of the drum beyond the inner edge of the vane alongsubstantially an entire length of the paddles.
 10. The system forrecycling glass of claim 9 in which the radially oriented paddles aredisposed circumferentially approximately 120 degrees apart.
 11. Thesystem for recycling glass of claim 9 in which the rotary drum washercomprises an inlet at one end thereof.
 12. The system for recyclingglass of claim 11 in which the rotary drum washer comprises a fluidoutlet at an opposite end thereof.
 13. The system for recycling glass ofclaim 12 in which the vane extends substantially between the fluid inletand the fluid outlet.
 14. The system for recycling glass of claim 11 inwhich the inlet is in communication with a hopper.